In the America of 2100, less elbow room

ST. LOUIS
— In the small village of Unalakleet, Alaska, some 170 miles shy of the Arctic Circle, the United States yesterday kicked off its national population count.

Census officials, including director Kenneth Prewitt, were scheduled to brave sub-zero cold to knock on doors and interview residents about their households. This year's national count, undertaken every decade, represents the largest US peacetime muster in history. By the time it ends later this year, demographers agree, census-takers will have documented a doozy of a demographic forecast.

Almost alone among the developed nations, the US population is growing robustly. By the end of the 21st century, when many demographers believe world population growth will begin to peak, the latest census projections show the US might have doubled its current size and still be growing. If those estimates hold true - a big if, admittedly - the US population would grow faster than Europe, Japan, even China.

The implications are enormous. Rising numbers might forestall worker shortages and ease the crises surrounding Medicare and Social Security. But growth would also pressure the environment, exaggerate urban sprawl, and gobble up world food and energy resources.

"It's important to think about [living with] an entire second United States," says Robert Engelman, vice president for research at Population Action International, a research and advocacy group in Washington. "You have to begin thinking while you're stuck in traffic having two cars for every car there is now. Where do we think this twice-the-population is going to live and work?"

To be sure, projecting populations a century ahead is highly speculative stuff. When demographers in 1900 tried to forecast a century ahead, many of them completely missed the growth spurt in the developing world and concluded - mistakenly - that the global population would peak somewhere around the 1960s.

"If you want to look 100 years ahead at US population, you should probably have Jules Verne rather than a demographer" do it, says Nicholas Eberstadt, a researcher at the American Enterprise Institute in Washington.

Nevertheless, current trends suggest powerful demographic changes ahead. Already, the United Nations projects that 61 nations (with about 44 percent of the world's population) have seen their fertility rates fall below what it would take to replace the previous generation (2.1 births per woman). By 2015, the number of such countries is projected to grow to 87 and include about two-thirds of the world's population, the UN says.

Most of those low-growth countries lie in the developed world. By 2050, for example, France's population will have grown only 2 percent and Italy's will have tumbled 28 percent, according to 1998 UN projections. Japan will have shrunk 17 percent. The US, meanwhile, will have grown 27 percent. (Forty-nine percent, according to the new census projections.)

Only a few developed countries can boast similar expected expansion, most notably Australia (39 percent) and Canada (38 percent). Even China, the world's most-populous nation, isn't expected to grow as fast (18 percent). Russia will shrink.

While some developing nations will grow faster America would remain by far the largest developed nation still growing.

"We're basically in a club of our own," says Mr. Eberstadt. "We have almost replacement fertility and we have a welcoming disposition to newcomers."

Clearly, immigration plays an important role. The new census projections assume the US will add nearly 1 million new immigrants a year, a sharp contrast to most developed nations, says Jeffrey Passel, a demographer at the Urban Institute in Washington.

The other main population booster - fertility - is harder to explain. Fertility rates have fallen dramatically in almost all parts of the world except sub-Saharan Africa. In the early 1950s, for example, the average European couple produced 2.6 children; today it produces only 1.4, according to the UN. North America's fertility rate also fell from 3.5 in the 1950s to 1.8 children in the 1970s. But since then, it has rebounded to the 1.9 to 2.0 range.

The US could change course by limiting immigration or stressing family planning more forcefully. But population experts disagree whether it should. Since 1900, the US population has tripled and yet, by almost any measure, today's Americans live longer, healthier, more comfortable lives, points out a report by the Cato Institute, a Washington research organization.

On the other hand, a continued rise could mean paved-over farmland, strained water supplies, and accelerated global warming. "We put about 20 to 30 times more carbon in the air than the average resident of a developing country," says Mr. Engelman. "The rest of the world has a stake in what happens to the population of the United States."